Along with increasing demands in recent years for miniaturization and higher speeds in the field of information processing machines, there have been advances with regard to narrowing the pitch of integrated circuits and grid arrays of pin terminals and in thinning of pin terminals. Likewise, in packaging of electronic parts such as integrated circuits, though direct soldering to boards is common, packaging using connectors and sockets in order to improve quality is increasing. Thus, there is an increasing need to make connectors and sockets thinner for packaging electronic parts in order to miniaturize information processing devices, and particularly, for use in portable electronic devices.
Presently, such contacts and sockets are thicker since the contacts, which are the portions that contact the pins of the electrical parts, are formed by punching using progressive metal dies and secured by press fitting each pin or line into an injection-molded housing. As such, they are not suitable for thinner devices. Likewise, along with miniaturization, as the walls of the plastic housings have become thinner, problems are associated with respect to the ability to injection mold thinner-walled housings and with respect to the strength of the thinner walls when securing the contacts.
Then, connectors and sockets which do not include contacts that are inserted in a three dimensional housing, and which instead include contacts arranged on a single film surface, were tried. Methods of injection molding film-type connectors and sockets by forming conductors in which contacts are linked and then inserting these conductors (U.S. Pat. Nos. 6,045,367 and 6,146,151) and a method of applying these to contact sheets were proposed. However, with these, a portion of the contact area was reduced by removing the linking portion (which linked the contacts with each other), and while there was a need to provide insulation between the contacts, there was a problem in that if portions of the contacts that are to be removed were provided, the minimum size of the contact size that is necessary to maintain a satisfactory spring load could not be guaranteed.
As a method of eliminating the process of removing the linking portion, there is a method of etching after attaching conductors to one side of a polyimide film in which numerous holes are provided (for example TAB, Tape Automated Bonding). The invention noted in U.S. Pat. No. 6,298,552 is an example of an application of that method. This method has a problem, however, in that the contacts peel off or otherwise come off during bending because the contact is bonded only by the strength of the surface connection. Likewise, there is also the problem that when polyimide is applied to one side and etching is done on the other surface, the cross-section becomes trapezoidal and since one edge would be sharpened, precision processing could not be performed and repeat durability would be decreased due to cracks generated at the sharpened edge. Furthermore, with this method, if the contacts were arranged in area arrays, only costly electroless plating could be used because individual contacts are electrically insulated.